This nautical astrolabe is thought to be among the earliest surviving nautical astrolabes and dates from about 1500−1520. Most nautical astrolabes had a carved mater (graduated circular element), unlike the solid and compact instrument shown here, which bears a resemblance to the astrolabes of Diogo Ribeiro (died 1533), a Portuguese cartographer and inventor who spent most of his life in Spain. The purpose of nautical astrolabes was to measure the altitude of the sun or a star above the horizon. Navigators could determine a ship’s latitude by knowing ...

Mulahhas fī al-Hay'a (Compendium of astronomy) by Sharaf al-Dīn Mahmūd ibn Muhammad ibn ‘Umar al-Jiġhmīnī (died circa 1221) is one of the most famous textbooks of astronomy ever produced in the Islamic world. The importance of the work is clearly indicated by the existence of thousands of copies of the text, some representing the autonomous tradition of the Mulahhas itself, others preserving the work as part of the many commentaries and even supercommentaries (commentaries on commentaries) that were produced in the centuries that followed its appearance. One well-known extensive ...

Pedro de Medina (1493–1567) was a cartographer, author, and a founder of marine science. He lived in Seville, the center of the Spanish ocean-going commerce and the starting point for ships headed to the New World. He worked in an environment shaped by the Casa de Contratación (House of Trade), the Spanish government agency that controlled exploration and colonization, although he was never employed by it. In 1545 Medina published his most important work, El arte de navegar (The art of navigation), an overview of existing knowledge on this ...